1. Field of the Invention
The present invention relates to paper machine clothing, and, more particularly, to a method for preparing a seam area for the clothing in an endless manner.
2. Description of the Related Art
A paper machine clothing (PMC) base fabric is typically manufactured with a specific set of design and quality specifications for a particular paper machine's performance requirements. These specifications include surface characteristics, open area, void volume, permeability and smoothness, among others.
A woven PMC base fabric can be woven “endless”. The fabric produced by this method can be referred to as a circular (or round) woven endless fabric. Alternatively, a woven PMC base fabric can be woven “flat”, and the free ends can then be joined. The fabric produced by this method can be referred to as a flat-woven fabric.
It is known to manufacture a woven press fabric having a flat-woven base fabric with a plurality of warp yarns forming seam loops along the ends of the fabric extending in a cross machine direction (CD), transverse to the machine direction (MD). The ends are then placed in end-to-end disposition in order to interdigitate the loops and a pintle wire is then inserted in the interdigitated loops to lock the ends together to bring the fabric into an endless form. For installation in a paper machine of the like, the two ends are separated such that the fabric can be pulled in its direction of movement into the machine, after which the two belt longitudinal ends can then be joined together again. The region of the seam in this case has a larger void area than the rest of the fabric, resulting in a differential dewatering in this area which may lead to marking of the fibrous web. In addition, the formation of seam loops on the base fabric results in increased production time and expense.
PCT Intl. App. No. PCT/GB89/00681 discloses a seam for a PMC base fabric in which a number of weft yarns are removed from the fabric at a fold location. The fabric is folded over at the fold location, sewed adjacent the fold location, interdigitated with loops from an adjacent fabric end, and a pintle wire is inserted through the interdigitated loops.
Further, experience has shown that the addition of a multifilament yarn in a seam zone (before the first CD yarn on the sheet side as disclosed in U.S. Pat. No. 5,476,123 (Rydin)) reduces sheet marking and improves seam durability. This method and more recent modifications work on circular woven endless base fabrics. It is thus known to add a multifilament yarn during an original circular weaving process on a loom.
Further, it is known to add a multifilament yarn to the seam after weaving by various methods for flat-woven base fabrics which are then converted into a laminate seam fabric. However, adding the multifilament yarn after weaving is time-consuming.
What is needed in the art is an improved process for preparing a seam area for a PMC base fabric.